It is known that materials acquire better machining properties during plastic deformation at a high ambient pressure. Such knowledge has been used for forging materials which are difficult to forge by performing the forging operation at a high ambient pressure. Such forging under high ambient pressure is described in U. S. Pat. No. 3,286,337. It is further known that the strength properties of materials can be improved by plastic deformation so that the yield stress point and ultimate strength of the materials are increased.